The purpose of the Bone Morphometry and Molecular Cytoimaging Core is to consolidate key personnel and equipment to provide a centralized resource facility to enhance collaborative and multidisciplinary investigations into the cellular and molecular mechanisms of osteoporosis. The Core will perform three different procedures in a high-quality, reliable and cost- effective manner: bone densitometry, bone histomorphometry and histostaining of bone tissue and bone marrow cells combined with in situ hybridization or in situ use of the reverse transcriptase-polymerase chain reaction (RT-PCR). The measurement of longitudinal changes in murine bone mineral density by dual-energy X-ray absorptiometry (DXA or DEXA), a technique we have developed for this Program, is used to determine the differences in bone density in the senescence accelerated mouse (SAM) and its hybrid progeny, the changes in bone density with age, gonadectomy and treatment in thee mice and other strains and the optimal time for ex-vivo cell cultures and histomorphometric analysis of undecalcified bone specimens. The noninvasive and precise nature of DEXA supersedes more traditional methods for the estimation of murine bone magnitude such as ashing or cortical width morphometry. This core will also obtain, fix, embed, section, stain and quantify the bone histomorphometric features of the axial and appendicular skeleton of young and old mice for the needs of the various projects. In preliminary work leading to this application, it has become evident that the concurrent performance on adjacent bone sections of RT-PCR for specific messages and histostaining with cell markers such as tartrate resistant acid phosphatase (TRAP) for osteoclasts, nonspecific esterase (NSE) for macrophages or alkaline phosphatase (ALP) for osteoblasts combined with tetracycline-labeled bone histomorphometry is required to characterize distinct subsets of bone and bone marrow cells, their gene expression patterns and their activity. This core has done over 400 murine DEXA measurements in-vivo over the past six months (sharing use of a clinical densitometer on weekends from 8 A.M. to 10 P.M. or on weekdays after 5 P.M.) and has processed 85 human bone biopsies and over 60 murine specimens for histomorphometric examinations in the past year. The bone laboratory is a CAP accredited facility with the ability to safely archive and store tissue and data. Bone densitometry and histomorphometric results will be appended to a relational database for prompt return to the principal investigators of each project.